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  <title>Generate a PBKDF2 key derivation of a supplied password</title>

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</div><hr /><div id="function.hash-pbkdf2" class="refentry">
 <div class="refnamediv">
  <h1 class="refname">hash_pbkdf2</h1>
  <p class="verinfo">(PHP 5 &gt;= 5.5.0)</p><p class="refpurpose"><span class="refname">hash_pbkdf2</span> &mdash; <span class="dc-title">Generate a PBKDF2 key derivation of a supplied password</span></p>

 </div>

 <div class="refsect1 description" id="refsect1-function.hash-pbkdf2-description">
  <h3 class="title">说明</h3>
  <div class="methodsynopsis dc-description">
   <span class="type">string</span> <span class="methodname"><strong>hash_pbkdf2</strong></span>
    ( <span class="methodparam"><span class="type">string</span> <code class="parameter">$algo</code></span>
   , <span class="methodparam"><span class="type">string</span> <code class="parameter">$password</code></span>
   , <span class="methodparam"><span class="type">string</span> <code class="parameter">$salt</code></span>
   , <span class="methodparam"><span class="type">int</span> <code class="parameter">$iterations</code></span>
   [, <span class="methodparam"><span class="type">int</span> <code class="parameter">$length</code><span class="initializer"> = 0</span></span>
   [, <span class="methodparam"><span class="type">bool</span> <code class="parameter">$raw_output</code><span class="initializer"> = false</span></span>
  ]] )</div>

 </div>


 <div class="refsect1 parameters" id="refsect1-function.hash-pbkdf2-parameters">
  <h3 class="title">参数</h3>
  <p class="para">
   <dl>

    
     <dt>
<em><code class="parameter">algo</code></em></dt>

     <dd>

      <p class="para">
       Name of selected hashing algorithm (i.e. <em>md5</em>,
       <em>sha256</em>, <em>haval160,4</em>, etc..) See
       <span class="function"><a href="function.hash-algos.html" class="function">hash_algos()</a></span> for a list of supported algorithms.
      </p>
     </dd>

    
    
     <dt>
<em><code class="parameter">password</code></em></dt>

     <dd>

      <p class="para">
       The password to use for the derivation.
      </p>
     </dd>

    
    
     <dt>
<em><code class="parameter">salt</code></em></dt>

     <dd>

      <p class="para">
       The salt to use for the derivation. This value should be generated randomly.
      </p>
     </dd>

    
    
     <dt>
<em><code class="parameter">iterations</code></em></dt>

     <dd>

      <p class="para">
       The number of internal iterations to perform for the derivation.
      </p>
     </dd>

    
    
     <dt>
<em><code class="parameter">length</code></em></dt>

     <dd>

      <p class="para">
       The length of the output string. If <em><code class="parameter">raw_output</code></em>
       is <strong><code>TRUE</code></strong> this corresponds to the byte-length of the derived key, if
       <em><code class="parameter">raw_output</code></em> is <strong><code>FALSE</code></strong> this corresponds to twice the
       byte-length of the derived key (as every byte of the key is returned as
       two hexits).
      </p>
      <p class="para">
       If <em>0</em> is passed, the entire output of the supplied
       algorithm is used.
      </p>
     </dd>

    
    
     <dt>
<em><code class="parameter">raw_output</code></em></dt>

     <dd>

      <p class="para">
       When set to <strong><code>TRUE</code></strong>, outputs raw binary data. <strong><code>FALSE</code></strong> outputs lowercase
       hexits.
      </p>
     </dd>

    
   </dl>

  </p>
 </div>


 <div class="refsect1 returnvalues" id="refsect1-function.hash-pbkdf2-returnvalues">
  <h3 class="title">返回值</h3>
  <p class="para">
   Returns a string containing the derived key as lowercase hexits unless
   <em><code class="parameter">raw_output</code></em> is set to <strong><code>TRUE</code></strong> in which case the raw
   binary representation of the derived key is returned.
  </p>
 </div>


 <div class="refsect1 errors" id="refsect1-function.hash-pbkdf2-errors">
  <h3 class="title">错误／异常</h3>
  <p class="para">
   An <strong><code>E_WARNING</code></strong> will be raised if the algorithm is
   unknown, the <em><code class="parameter">iterations</code></em> parameter is less than or
   equal to <em>0</em>, the <em><code class="parameter">length</code></em> is less
   than <em>0</em> or the <em><code class="parameter">salt</code></em> is too long
   (greater than <strong><code>INT_MAX</code></strong><em> - 4</em>).
  </p>
 </div>


 <div class="refsect1 examples" id="refsect1-function.hash-pbkdf2-examples">
  <h3 class="title">范例</h3>
  <p class="para">
   <div class="example" id="example-809">
    <p><strong>Example #1 <span class="function"><strong>hash_pbkdf2()</strong></span> example, basic usage</strong></p>
    <div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br />$password&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #DD0000">"password"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$iterations&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">1000</span><span style="color: #007700">;<br /><br /></span><span style="color: #FF8000">//&nbsp;Generate&nbsp;a&nbsp;random&nbsp;IV&nbsp;using&nbsp;mcrypt_create_iv(),<br />//&nbsp;openssl_random_pseudo_bytes()&nbsp;or&nbsp;another&nbsp;suitable&nbsp;source&nbsp;of&nbsp;randomness<br /></span><span style="color: #0000BB">$salt&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">mcrypt_create_iv</span><span style="color: #007700">(</span><span style="color: #0000BB">16</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">MCRYPT_DEV_URANDOM</span><span style="color: #007700">);<br /><br /></span><span style="color: #0000BB">$hash&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">hash_pbkdf2</span><span style="color: #007700">(</span><span style="color: #DD0000">"sha256"</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$password</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$salt</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$iterations</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">20</span><span style="color: #007700">);<br />echo&nbsp;</span><span style="color: #0000BB">$hash</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
    </div>

    <div class="example-contents"><p>以上例程的输出类似于：</p></div>
    <div class="example-contents screen">
<div class="cdata"><pre>
120fb6cffcf8b32c43e7
</pre></div>
    </div>
   </div>
  </p>
 </div>


 <div class="refsect1 notes" id="refsect1-function.hash-pbkdf2-notes">
  <h3 class="title">注释</h3>
  <div class="caution"><strong class="caution">Caution</strong>
   <p class="para">
    The PBKDF2 method can be used for hashing passwords for storage. However, it
    should be noted that <span class="function"><a href="function.password-hash.html" class="function">password_hash()</a></span> or
    <span class="function"><a href="function.crypt.html" class="function">crypt()</a></span> with <strong><code>CRYPT_BLOWFISH</code></strong> are
    better suited for password storage.
   </p>
  </div>
 </div>


 <div class="refsect1 seealso" id="refsect1-function.hash-pbkdf2-seealso">
  <h3 class="title">参见</h3>
  <p class="para">
   <ul class="simplelist">
    <li class="member"><span class="function"><a href="function.crypt.html" class="function" rel="rdfs-seeAlso">crypt()</a> - 单向字符串散列</span></li>
    <li class="member"><span class="function"><a href="function.password-hash.html" class="function" rel="rdfs-seeAlso">password_hash()</a> - Creates a password hash</span></li>
    <li class="member"><span class="function"><a href="function.hash.html" class="function" rel="rdfs-seeAlso">hash()</a> - Generate a hash value (message digest)</span></li>
    <li class="member"><span class="function"><a href="function.hash-algos.html" class="function" rel="rdfs-seeAlso">hash_algos()</a> - Return a list of registered hashing algorithms</span></li>
    <li class="member"><span class="function"><a href="function.hash-init.html" class="function" rel="rdfs-seeAlso">hash_init()</a> - Initialize an incremental hashing context</span></li>
    <li class="member"><span class="function"><a href="function.hash-hmac.html" class="function" rel="rdfs-seeAlso">hash_hmac()</a> - Generate a keyed hash value using the HMAC method</span></li>
    <li class="member"><span class="function"><a href="function.hash-hmac-file.html" class="function" rel="rdfs-seeAlso">hash_hmac_file()</a> - Generate a keyed hash value using the HMAC method and the contents of a given file</span></li>
   </ul>
  </p>
 </div>


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